A conventional gas turbine engine includes various rotor blades in the fan, compressor, and turbine sectors thereof, which are removably mounted to respective rotor discs. Each of the rotor blades includes a blade root at the radially inner end thereof. Each of the blade roots conventionally includes one or more pairs of lobes which can axially slide into and be retained in one of a plurality of axially extending attachment slots in the periphery of the rotor disc, thereby forming the attachment of the rotor blade. In a cooled turbine rotor assembly, the attachment or blade root of each rotor blade defines a cooling air entry cavity therein for receiving cooling air and bringing cooling air into the airfoil of the rotor blade for cooling same. In order to maintain the structural stiffness of the attachment, a given number of divider walls or ribs extending within the cavity is usually required because a centrifugal load which is born by the blade attachment, is generated as the blade rotates around the main engine axis. Nevertheless, conventional divider walls or ribs have limited effect. The centrifugal load generated by the high rotational speed of the rotor assembly results in not only large compressive stresses on the ribs, but also buckling and shear effects which can initiate cracks in the blade attachment structure.
Accordingly, there is a need to provide an improved blade root structure for cooled turbine rotor assemblies of gas turbine engines in order to meet the demanding requirements of various aspects of high efficiency gas turbine engines.